The present invention relates to multiple-piece swage type fasteners including a pin and a collar and more particularly to such fasteners having a flexible connection between the pin and collar to facilitate pre-assembly of the fastener components with the workpieces to be secured together.
The present invention generally relates to two-piece swage type fasteners or lockbolts of the types illustrated in U.S. Pat. No. 3,915,053 to J. Ruhl, issued Oct. 28, 1975, U.S. Pat. No. 2,531,048 to L. Huck, issued Nov. 21, 1950, U.S. Pat. No. 4,472,096 to J. Ruhl and R. Dixon, issued on Sept. 18, 1984, U.S. Pat. No. 4,342,529 to W. J. Smith issued on Aug. 3, 1982, and U.S. Pat. No. 3,295,404 to D. M. Baker, issued on Jan. 3, 1967. All of the above patents can be considered as prior art relative to the present invention.
The fastener of the present invention, as with the prior art noted, includes a pin and a collar adapted to be swaged into lock grooves in the pin in response to a preselected relative axial force applied between the pin and collar.
In many commercial applications, two-piece threaded fasteners are used and are installed in two or more steps. Thus it is common to secure a structure first by attaching the associated members with the fasteners loosely engaged. This facilitates adjustment and/or alignment of the structural members to a final, desired orientation. Next the fasteners are tightened to a preselected final torque. A traditional problem with torque applied threaded fasteners is that the final clamp load attained is generally unpredicatable due to frictional and other factors i.e. friction between nut and engaged workpiece surface, friction in the engaging threads, etc. Two-piece swage type fasteners, however, are not confronted with such frictional problems and hence can provide more uniformly predictable clamp loads. However, the swage type fasteners have not been capable of providing the initial assembly or fit up available with threaded fasteners and still provide a final clamp with only a second, final installation step. Prior threaded swage and/or crimp type fasteners would require extra steps or complex tooling. For example, a threaded crimp type fastener would not provide the same flexibility without complex installation tools; see for example the U.S. Pat. No. 3,421,562 to J. F. Orloff et al issued Jan. 14, 1969. While the latter fastener would permit an initial assembly similar to a conventional threaded fastener, the final installation would require either separate additional steps of final torquing and crimping or a complex tool capable of performing the latter steps in sequence.
In the present invention the lock grooves of the pin can be in the form of annular grooves or a helical male thread. The collar is provided with a flexible tab-like construction of a preselected circumferential extent such that an initial assembly and limited clamp can be accommodated. In addition the flexible tab-like structure is shaped such as to provide for ease of assembly of the collar onto the pin while providing a higher resistance to disassembly. At the same time, the tab permits disassembly, prior to final installation, in those applications where this may be desired. The tab structure is constructed such that, in response to the relative axial force applied to set the fastener and at a level prior to the initiation of collar swage into the pin lock grooves between the pin lock ridges, it will deform whereby the collar will be free to move axially over the pin and to respond to the installation loads in the same manner as a collar without such a tab structure. In addition the flexible tab is purposely located at either extremity of the collar where its effect on lock groove fill via the swaged collar will be minimal and hence the tab structure, while inhibiting the collar from moving off the pin prior to swage, will not appreciably affect the strength of the installed fastener. Thus the fastener permits the workpieces to be pre-assembled and finally secured together with the desirable high clamp loads available with swage type fasteners.
While the noted patent to Baker, supra, shows the use of a retaining ring to hold a pin and collar together, it does not teach the tab-like structure having features as noted above; in addition the present invention provides a unique and simple means of constructing the tab-like structure and collar combination.
While in one form of the invention the final installation of the fastener can be accomplished with a conventional pull tool, in another form a stump type version of the fastener could be utilized with the final installation effectuated by a squeeze type tool.
Thus it is an object of the present invention to provide a novel two-piece swage type fastener for a fastened joint with a pin having a lock groove and ridges section with a plurality of lock grooves and with a collar adapted to be swaged into the lock groove section and having a flexible tab-like structure engageable with the lock grooves and allowing for the pin, collar and the joint to be held together, prior to swage, in a non-permanent pre-assembly.
It is another object of the present invention to provide a novel two-piece swage fastener of the type noted in the preceding object in which the tab-like structure on the collar is adapted to be deformed out of the lock grooves by a preselected axial load which is less than that at which collar deformation in swage is initiated.
It is another object of the present invention to provide a novel two-piece swage fastener of the type noted in which the tab-like structure is located at a position to minimize its affect on the lock between the collar and pin.
It is another general object of the present invention to provide a novel two-piece swage type fastener and a method of making same.